<template>
  <div class="pagination" >
    <button :disabled="pageNo===1" @click="$emit('pageInfo',pageNo-1)">上一页</button>
    <button 
    v-if="continueNum.start>1" 
    @click="$emit('pageInfo',1)"
    :class="{active:pageNo===1}"
    >1</button>

    <button v-if="continueNum.start>2">···</button>

    <button 
    v-for="(page, index) in continueNum.end" :key="index"
    v-if="page>=continueNum.start"
    @click="$emit('pageInfo',page)"
    :class="{active:pageNo===page}"
    >
      {{ page }}
    </button>

    <button v-if="continueNum.end<totalPage-1">···</button>
    <button 
    v-if="continueNum.end<totalPage"
    @click="$emit('pageInfo',totalPage)"
    :class="{active:pageNo===totalPage}"
    >{{ totalPage }}</button>
    <button 
    :disabled="pageNo===totalPage" 
     @click="$emit('pageInfo',pageNo+1)">下一页</button>

    <button style="margin-left: 20px">共{{ total }}条</button>
 
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props: ["pageNo", "pageSize", "total", "continues"],
  methods: {},
  computed: {
    // 总共多少页
    totalPage() {
      // 向上取整
      return Math.ceil(this.total / this.pageSize);
    },

    // 计算出连续的页面的起始数字与结束数字
    continueNum() {
      const { continues, totalPage, pageNo } = this;
      let start = 0,
        end = 0;
      if (continues > totalPage) {
        // 不正常情况：连续页码数大于总页数
        start = 1;
        end = this.totalPage;
      } else {
        // 正常情况：连续页码数小于总页数
        start = pageNo - parseInt(continues / 2);
        end = pageNo + parseInt(continues / 2);
        // 边界处理，当前页处于边界时
        if (start < 1) {
          start = 1;
          end = continues;
        }
        if (end > totalPage) {
          end = totalPage;
          start = totalPage - continues + 1;
        }
      }
      return { start, end };
    },
  },
  mounted() {},
};
</script>

<style lang="css" scoped>
.pagination {
  text-align: center;
}
.pagination button {
  margin: 0 5px;
  background-color: #f4f4f5;
  color: #606266;
  outline: none;
  border-radius: 2px;
  padding: 0 4px;
  vertical-align: top;
  display: inline-block;
  font-size: 13px;
  min-width: 35.5px;
  height: 28px;
  line-height: 28px;
  cursor: pointer;
  box-sizing: border-box;
  text-align: center;
  border: 0;
}
.pagination button[disabled] {
  color: #c0c4cc;
  cursor: not-allowed;
}
.pagination button.active {
  cursor: not-allowed;
  background-color: #409eff;
  color: #fff;
}
.active {
  background: skyblue;
}
</style>
